Cross sections have been measured for methylhydrazine (CH3NHNH2) reactions with O+, CO+, CO2+, and NO+ at collision energies ranging between 1 and 20 eV (center of mass) in an octopole guided-ion-beam apparatus. As was the case for similar reactions involving hydrazine, charge transfer and dissociative charge transfer occur in each reaction. The total reaction cross section is on the order of 50-100 Angstrom(2), and the amount of CH3NHNH2+ fragmentation in each case depends upon both the exothermicity of the charge transfer and the availability of internal degrees of freedom in the incident primary ion. The product ion kinetic energies are primarily thermal or near-thermal in the laboratory frame, as is often found for reactions involving efficient exothermic charge transfer. Charge transfer cross sections are also reported for the CO+ + H2O and CO2+ + H2O systems for the 0.2 less than or equal to E(cm) less than or equal to 6 eV range.